gitlab:db:lock_writes should lock writes on tables partitions as well

Lock-writes

We have the rake task gitlab:db:lock_writes to lock writes on all the legacy tables (gitlab_main tables on ci database, and gitlab_ci on main databaes).

This rake task was meant to lock the writes on the partitioned tables, but not their partitions.

The problem

As part of the post-staging/production legacy tables truncation analysis: #376305 (closed)

We discovered that some tables had some tables had some partitions locked-for writes and some partitions are not locked for writes. For example security_findings on the ci database had the partition security_findings_1 locked for writes, while the partition security_findings_2 was not locked for writes. This is simple due to the fact that some partitioned happened to be tables before when we locked writes on the tables. And these locks persisted on the tables when they were converted into partitions

To understand why this was happening in details, the issue had all the details about this with all the relevent MRs.

The goal

The goal of this issue to modify the rake task gitlab:db:lock_writes to lock the writes on the tables partitions as well.

Special Case Scenario to pay attention to

The rake task gitlab:db:lock_writes skips any tables that are already locked for writes. But this should be modified to look into the partitions as well. In another words, it should not assume that table partitions are locked for writes as well

Relevant topics/links

This relevant MR recently has been implemented to handle truncating tables and and their locked partitions as well, which is the issue that we faced on staging and production.
The source code of the gitlab:db:lock_writes rake task: https://gitlab.com/gitlab-org/gitlab/-/blob/master/lib/tasks/gitlab/db/lock_writes.rake

CC: @tkuah @rutgerwessels